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The Many Health Benefits of Intermittent Fasting

"Start small, do it safely, and you can get some of these amazing benefits from intermittent fasting."

We've talked quite a bit about *what* we should eat as part of a healthy lifestyle. Now let's talk about *when* we eat! Today Dr. Keller Wortham, MD, is talking about a diet trend that's been around for a long time but has recently enjoyed the health spotlight — intermittent fasting. We'll talk about what intermittent fasting is, the various health benefits associated with it, some different approaches to intermittent fasting, and how to do it safely.

Video Highlights

  • 01:11: Three Approaches to Intermittent Fasting
  • 03:20: Why Do People do Intermittent Fasting?
  • 04:22: Benefits of Intermittent Fasting
  • 19:12: Intermittent Fasting is Not for Everyone
  • 20:36: Wrap-Up

The first thing to say about intermittent fasting, is that it’s not actually a new thing. You probably know that fasting has been around a long time. It's been used in many different cultures, religions, and periods of life as a way to cleanse and heal the body.  So today, we're looking at the modern intermittent fasting trend, discussing whether it has real health benefits, and providing some tips on how to do it safely. 

Three Approaches to Intermittent Fasting

Intermittent fasting is basically going through scheduled periods when you eat and periods when you fast. There are a lot of different strategies to engage in intermittent fasting, but for the most part these days, there are three primary approaches. 

The 16:8 Approach

The first approach, which we're referring to as the 16 and 8 approach, basically means trying to fast during portions of each day. People using this approach fast for 16 hours of the day and eat during the other eight. For example, you might skip breakfast, and start eating at 11:00, then only eat for the next eight hours until maybe 7:00, at which point you stop eating for the day. So you’re essentially reducing the window of time during which you eat. Some people will make that more severe and only eat during a six-hour window. So you’re basically reducing your caloric intake to a certain specific window during each day.

The 5 and 2 Approach

The 5 and 2 basically means that you are eating normally for five days of the week and then fasting or avoiding caloric intake for the other two days. The two fasting days should not be consecutive. So, you might pick Tuesday and Saturday to fast — or any two days, so long as they’re not right next to each other.

Alternate Day Fasting

A third strategy for intermittent fasting is what's called ADF or alternate day fasting. This is the most extreme version. If you’re doing ADF, you are eating for a 12-hour period in one day and then you're not eating that night or the entire next day. So it’s basically 12 hours of eating, and 36 hours of not eating. You might eat Monday, not eat Tuesday, eat Wednesday, not eat Thursday, and so on.

So those are the three main categories of intermittent fasting.

Why Do People do Intermittent Fasting?

So you may be thinking, “I love food. Why would I deprive myself of food?”  Or you may have heard that fasting is actually bad for you because your body needs calories, it needsprotein for muscles, and it needs healthy fats, or that you don't want to deprive our body of calories because that can shut the metabolism down. A lot of these pieces of information that are out there might make us think that maybe intermittent fasting might not be a good idea. However, there really are some benefits to intermittent fasting. In fact, there have been many studies that have shown significant benefits especially in certain populations.

Benefits of Intermittent Fasting

One thing to recognize is that our bodies were programmed to be able to fast. We weren't genetically and metabolically designed to eat three meals a day, and cookies and cakes in between, and snacks all over the place. Our bodies evolved at a time when food was not as plentiful, or readily available in the amounts that we get today. Humans had to be able to survive droughts, harsh winters, and migrations. In other words, we are programmed to be able to handle intermittent fasting. So, it makes sense that there could then be some benefits programmed in there as well. Some of those benefits might just change your mind about intermittent fasting.

Weight Loss

This is probably the most obvious one. You're fasting — you're eating less food, and therefore you're going tolose weight. It seems like a lot of people know they need to lose weight, and just can't seem to do it. One of the good things about intermittent fasting is it's very structured. You have a period where you can eat and then you have a period where you're not supposed to, and when you're in that eating period, you can eat basically anything you want. There's no counting calories, or worrying about different kinds of food. Doctors have seen that if they give someone an intermittent fasting regimen, they often find it easier to adhere to than a diet, because of the structure, and because they don't have to limit themselves on eating days. We've also seen that people actually consume 37% fewer total calories, even when they have the ability to eat as much as they want on those non-fasting days. They also tend to choose healthier foods on those non-fasting days. So it can actually make it easier for people to lose weight. Additionally, when people get used to fasting after an initial transition period, they often find they don't feel as hungry on those fasting days, and can even feel really good and energized.

Some people have a fear that fasting will slow down their metabolism, but when you're doing it right — using one of the strategies listed above, as opposed to going weeks without eating — there can actually be anincrease in metabolism by up to 14%. That means you're burning a lot more calories, and again, you can eat what you want during non-fasting periods. So, don't worry about your metabolism slowing down with intermittent fasting. 

Also, the weight loss that occurs tends to be central adiposity weight loss — that means fat that accumulates around the central organs. That fat is worse for the body, worse for the heart, and increasesinflammation in the body. People doing intermittent fasting can lose 4% to 7% of their waist circumference. If you have a larger waist that can mean a couple inches off your waist just by doing intermittent fasting. 

Improves Crucial Hormone Levels

For those of you who might not be looking to lose weight, there are plenty of other benefits.  So, let's dive into the number two: intermittent fasting improves crucial hormone levels, including insulin and HGH. Insulin is a hormone involved in fat storage, which plays a major role indiabetes. When our insulin levels are high, we tend to store more fat, and our bodies increase inflammation, so when we're storing more fat, obviously we're going to gain weight.  But when we intermittently fast, our insulin levels drop because the insulin becomes more sensitive and is able to perform its function better. As your insulin levels drop, you get a lot of benefits out of that including reduced inflammation, reduced risk of diabetes, and reduced weight gain. 

The other hormone that we just mentioned is human growth hormone (HGH), which also increases when you undergo intermittent fasting. Human growth hormone is great for the body: it helps improvemuscle mass, and lean body mass, it helps repair damaged tendons and ligaments, and it even helps with yourskin. So intermittent fasting can improve even the way that you look.

Combats Aging and Reduces Oxidative Stress

Intermittent fasting can actually have anti-aging properties! They've done studies which demonstrate that when you undergo intermittent fasting, the expression of certain genes within your body changes. Our genes are the computers within each cell and they're constantly regulating differentmetabolic functions within the body, and the way those genes are expressed with what potency or frequency really has an effect on how our bodies evolve, how they're driven, what our metabolism does, and how we're repairing things. When people undergo intermittent fasting, some of the genes upregulate in their expression. These are the genes that are protective to our bodies — they help clean out debris, and reduce metabolic damage to the cells, and oxidative stress. Oxidative stress is just the natural stress that our body undergoes just by being here on the planet and metabolizing things. When we metabolize things, we oxidate — it's basically the rusting of our bodies. Over time, oxidative stress damages cells, causes inflammation and hurts parts of our body. When we intermittently fast, we reduce that oxidative stress.  

One of the reasons we think all of that happens is something calledautophagy.Autophagy is the process of ridding the body of the toxic debris left over from your metabolism.  So, your body is basically going through a process of housecleaning. When you intermittently fast, you're helping your body clean house faster, while reducing inflammation, and that's going to be really great for your body. 

Decreases Risk of Diabetes

This one might seem obvious, because we know intermittent fasting increases weight loss, and makes insulin more sensitive, and we knowtype 2 diabetes is about insulin resistance — meaning your body isn't using insulin the way it's supposed to and your pancreas starts to get burned out because it's trying to make too much insulin. So, we know that by intermittent fasting you can greatly reduce your risk for type 2 diabetes. Increasingblood sugar by a mere 6% can increase the risk of developing diabetes by up to 20% to 30%. And this is a disease that is affecting literally millions of people in the U.S. alone. So intermittent fasting is a way to reduce that risk for diabetes. If you're pre-diabetic, or if you already have diabetes, talk with your doctor — intermittent fasting might be a safe way to help get you out of a diabetic state. 

Reduces Risk of Heart Disease

Intermittent fasting actually helps reduce your risk of a heart attack, stroke, or heart failure and there are multiple reasons for that. Number one, you're reducing the inflammation which can clog your blood vessels.

Secondly, intermittent fasting alsoregulates cholesterol; it increases good cholesterol, and reduces bad cholesterol. So those two things alone really help reduce the oxidative stress (the rusting of your arteries), and protects the heart from those aspects of metabolism.  

Reduces Risk of Cancer

Intermittent fasting has been shown to reduce cancer risk. It seems like we’re battling cancer on all sides these days. Statistically, that might be because we're getting better at diagnosing certain cancers, and people are living longer. But we’ve got cancer affecting the breasts, lungs, colon, prostate, and much more. Anything we can do that can reduce cancer risk is a tool we should certainly be looking at, and it's thought that intermittent fasting can reduce cancer risk in a few ways: 

  • We're reducing oxidative stress, which is just bad for the body in general.  
  • We talked about the changes in gene expression. We're starting to improve and increase the expression of certain genes that are kind of our housecleaning genes, helping us get rid of bad cells in the body. 
  • We also talked about insulin and how intermittent fasting can reduce insulin levels.  Insulin is a kind of growth hormone that can simulate the improper growth of certain tumors.  

So, for those reasons we think that intermittent fasting can reduce cancer.

In fact, they have done some small studies on patients who were undergoing chemotherapy for cancer and chose to fast before their chemotherapy regimens, and actually found that the fasting helped improve their symptoms during the chemotherapy. These patients experienced fewer side effects and better results of the chemo when they were using to battle their cancers. So, again, if you do have cancer, talk to your doctor about fasting. This is a very new field of study, so there are no guaranteed results, but it may be something to consider and discuss with your healthcare provider.  

Improves Brain Health

Intermittent fasting is also good for your brain!  Of course we know that we need good food for our brains — we need good cholesterol, and good oils. But again, we're not talking about fasting for days on end and depriving ourselves of food long-term, we’re talking about short periods of fasting, which has been shown to actually help brain function. Researchers believe  that improvement is a result of the other benefits we’ve listed here — lower insulin levels, better gene expression, less inflammation — but also, intermittent fasting has been shown to increase new nerve growth in rats. In other words, we might actually be able to regenerate some of our nervous tissues. 

We've also seen increased levels of specific chemicals like brain derived neurotropic factor. Increased levels of this chemical are great for our brains, while decreased levels can lead to brain issues likedepression ordementia. In fact, it's been thought that intermittent fasting can even reduce the risk of Alzheimer’s. Alzheimer's is a devastating issue that's still not understood and not necessarily completely preventable. But if you have Alzheimer's in your family, intermittent fasting could be a potential tool to reduce your risk.  In fact, some Alzheimer’s patients they have tried intermittent fasting and it’s been found that 9 out of 10 patients who already have Alzheimer's see animprovement in cognitive abilities and a decrease in symptoms as a result. 

Increases Longevity

Considering all the benefits we just talked about, this is a rational conclusion. If you're reducing inflammation, reducing your risk of diabetes and heart disease, upregulating gene expression, improving your brain health, and combating accelerated aging, it makes sense that you’re likely tolive longer. In studies using rats, researchers found that intermittent fasting can extend the rat’s life by up to 80%. That’s mind-blowing! So, if you take all of these cumulative benefits of intermittent fasting, they may actually help you  extend your life. We'll know more as we get more controlled studies involving humans and move into the future, but it's definitely something to think about. 

Intermittent Fasting is Not for Everyone

Hopefully this has helped illuminate why intermittent fasting is gaining so much steam, but we do have some parting words. 

There are some studies that show that it might be better for men than women, especiallypremenopausal women who are still having their period because intermittent fasting can throw off your menstrual cycle, which is not a great thing. 

Also, there are certain populations including children and adolescents, who should not intermittent fasting, because they need to be eating all the time. This is because their brains and bodies are in major development. 

Elderly people should be careful, because they are often already calorically deficient.  So, you don't want to be taking more calories out of an elderly person’s diet, especially if they're not getting a good baseline amount of calories. 

People with type 1 diabetes or with bad type 2 diabetes who were already on certain medications may not want to do it, because it could reduce blood sugar too much. If you fall into one of these populations, you should work with your doctor to make sure you don’t put yourself at risk for certain issues.

In general though, researchers have found that even six months into an intermittent fasting regimen, most people have very few side effects or none at all. Some of the things people might worry about like low white blood cell counts or low bone density, have not been found to be a result of intermittent fasting.


In conclusion, intermittent fasting may be a useful tool for your life. You don't have to go right into the deep end and start fasting every other day. Maybe start with an intermittent fasting period where you're just doing that eight-hour window every day, or every other day, or even just try one day a week where you try not eating anything. 

Keep in mind that you can still drink when you're in the fasting period.  You should be drinking water always, and you can havecaffeinated beverages like coffee and tea.  You don't want to be using sweeteners orartificial sweeteners because they're very bad for shifting around some of your metabolic processes, so just stick with water and non-caloric and non-artificially sweetened beverages. So start small, do it safely, and you can get some of these amazing benefits from intermittent fasting.

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